I just remember first hearing the phase (around here) referring to lagging titles.
I understand any title can be fast-tracked.

Now that most titles have reached at least 1968 there are fewer titles seriously lagging behind.
Since titles like SA Doom, Ka-Zar & Inhumans would be 'one & done'--they wouldn't need to be fast-tracked just 'tracked'image

I do find it odd that Shield is both pre 1967 and has a super popular artist/writer and hasn't been done in well over a year. Also the Buscema Subby issues seem overdue.